well the weight of a nickel is about 10 grams. a truck cam do 12 tonnes for a six wheeler or 28 tonnes for a 22 wheeler with 3 axles. thats 600k coins for the 6 wheeler or 2.8 million for the 22 wheeler. am in Kenya so my calculations may not make complete sense, but I estimated for a fact you can't pack metal past 75cm high despite size of of vehicle. thus totally wrong.
Have you considered whether weight might be the limiting factor on number of coins in a truck rather than volume?
Thanks for the comments. It is actually a space and volume problem, as you cannot be sure that the weight of the coins can actually fit in a truck either, unless you've made both calculations.